The woman who stared at the sun Alex Gendler
In the spring of 1944, Tokyo residents
experienced numerous aerial attacks
from Allied bombers.
Air raid sirens warned citizens
to get indoors
and preceded strategic blackouts
across the city.
But 28-year old Hisako Koyama
saw these blackouts as opportunities.
Dragging a futon over her head
for protection,
Koyama would gaze at the night sky,
tracking all sorts
of astronomical phenomena.
However, her latest endeavor required
the light of day.
By angling her telescope towards the sun,
Koyama could project the star’s
light onto a sheet of paper,
allowing her to sketch
the sun’s shifting surface.
She spent weeks recreating this set up,
tracking every change she saw.
But while Koyama didn’t know it,
these drawings were the start
of one of the most important records
of solar activity in human history.
To understand exactly what Koyama
saw on the sun’s surface,
we first need to understand
what’s happening inside the star.
Every second,
trillions of hydrogen atoms
fuse into helium atoms
in a process called nuclear fusion.
This ongoing explosion maintains
the sun’s internal temperature
of roughly 15 million degrees Celsius,
which is more than enough energy
to transform gas
into churning pools of plasma.
Plasma consists of charged particles
that produce powerful magnetic fields.
But unlike the stable charged particles
that maintain magnetic activity on Earth,
this plasma is constantly in flux,
alternately disrupting and amplifying
the sun’s magnetic field.
This ongoing movement can produce
temporary concentrations
of magnetic activity
which inhibit the movement of molecules
and in turn reduce heat in that area.
And since regions with less heat
generate less light,
places with the strongest magnetic fields
appear as dark spots
scattered across the sun’s surface.
These so-called sunspots
are always moving,
both as a result of plasma
swirling within the sphere,
and the sun’s rotation.
And because they’re often
clustered together,
accurately counting sunspots and tracking
their movement can be a challenge,
depending greatly on the perception
and judgment of the viewer.
This is precisely where Koyama’s
contributions would be so valuable.
Despite having no
formal training in astronomy,
her observations and sketches
were remarkably accurate.
After sending her work
to the Oriental Astronomical Association,
she received a letter of commendation for
her dedicated and detailed observations.
With their support, she began to visit
the Tokyo Museum of Science,
where she could use a far superior
telescope to continue her work.
Koyama soon joined the museum’s staff
as a professional observer,
and over the next 40 years,
she worked on a daily basis,
producing over 10,000 drawings
of the sun’s surface.
Researchers already knew magnetic currents
in the sun followed an 11 year cycle
that moved sunspots in a butterfly shaped
path over the star’s surface.
But using Koyama’s record,
they could precisely follow
specific sunspots and clusters
through that journey.
This kind of detail offered a real-time
indication of the sun’s magnetic activity,
allowing scientists to track
all kinds of solar phenomena,
including volatile solar flares.
These flares typically emanate
from the vicinity of sunspots,
and can travel all the way
to Earth’s atmosphere.
Here, they can create geomagnetic storms
capable of disrupting long range
communication and causing blackouts.
Solar flares also pose a major risk
to satellites and manned space stations,
making them essential to predict
and plan for.
During an interview in 1964,
Koyama lamented that her 17 years
of observation had barely been enough
to produce a single butterfly record
of the solar cycle.
But by the end of her career,
she’d drawn three and a half cycles—
one of the longest records ever made.
Better still, the quality of her
drawings was so consistent,
researchers used them as a baseline
to reconstruct the past 400 years
of sunspot activity
from various historical sources.
This project extends Koyama’s legacy
far beyond her own lifetime,
and proves that science is not built
solely on astounding discoveries,
but also on careful observation
of the world around us.